Aircraft pilots use information regarding the location of potentially hazardous weather to decide on the routing to their destination. This information can come from a number of sources—such as pre-flight weather briefing, ground-based weather radar data, or on-board weather radar. Pilots use this information to decide if the weather will make it necessary to divert from the planned route. Generally this information provides location of weather at the present time, or earlier depending on the latency of the weather data. Since weather is often moving horizontally, the information on the location of the weather may not correspond to its location when the aircraft is close enough to be affected by the weather.
There has been a great deal of work done by numerous organizations on the tracking of hazardous weather. Tracking is typically done by identifying features that are recognizable over some period of time, and observing the movement of these features. These features are typically detected using radar. Convective weather shows significant variation in radar reflectivity—and also is responsible for much of the weather-related hazard pilots wish to avoid—so convection more readily produces identifiable features that can be tracked. By observing the change in position of a convective cell over time, the velocity vector of the cell can be estimated.
Cell tracking is often applied to ground-based weather radar data. The goal is to determine if a hazardous storm cell is moving in the direction of businesses, homes, farms, etc. that might suffer damage as a result. Conveying the information regarding cell motion on a plan view display typically involves drawing a vector from the current cell location and extending the vector in the direction of motion. The length of the vector shows the expected distance that the cell will travel in a fixed period of time. The user of this information compares the displayed cell motion with the location of assets of concern (which typically are fixed in location). If the convection was seen to be moving toward a location of interest, dividing the distance from the cell to that location by the cell speed provides the expected time of arrival of the weather.
For an aircraft pilot, the use of cell track information involves determining if the convective cell will require a diversion from the planned route. This determination is complicated by the fact that the aircraft is in motion. So the pilot must determine if a cell will intersect the planned route at the time that the aircraft is at or near that point. This requires some time-consuming calculation on the part of the pilot by considering the speed and direction of the aircraft and the speed and direction of the convection to make the determination of whether a diversion should be anticipated.